Process for effecting ring closure by means of hydrofluoric acid



Patented Get. 7, 1941 PROCESS FOR EFFECTING RING CLOSURE BY MEANS OF HYDROFLUOBIC ACID John M. Tinker, Penna Grove, and Viktor M.

Weinmayr, Pitman, N. J., and Adrian L. Llnch, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation 0! Delaware No Drawing. Application December 28, 1939,

. Serial No. 311,292

8 Claims.

This invention relates to a process for preparing organic compounds. The invention relates more particularly to an improved process for effecting ring closure of polynuclear aromatic compounds to form carbocyclic or heterocyclic derivatives.

It is well known that polynuclear aromatic compounds such as dinaphthyl, dianthraquinonyls, dibenzanthronyls, dianthrimides, benzanthronyl aminoanthraquinones, dibenzoylnaphthalenes, etc., are capable of ring closure to form compounds of higher order, ring. systems. Ring closure of these compounds is usually effected by means of alkaline or acid condensing agents. Some of these compounds can be ring closed only by alkaline condensing agents, some only with acid condensing agents, while others may be ring closed with either alkaline or acid condensing agents, although in certain cases the final products formed differ depending upon the type of ring closing agent employed.

Concentrated or fumingsulfuric acid, aluminum chloride, phosphorus pentoxide, phosphorus chlorides, halogen-sulfonic acids, or alkaline reagents, such as sodamide or alcoholic caustics are examples of the ring closing agents heretofore employed in the preparation of the higher molecular weight polynuclear aromatic compounds.

With these reagents, however, in many cases undesirable side reactions take place with the result that the yield of desired final product is low Inmany cases, where chlorosulfonic acid or oleum is employed sulfonation takes place such as inthe ring closure of dinaphthyl, giving high yields of sulfonic acids and very low yields of perylene.

It is an object of this invention to provide an I improved process for effecting ring closure of vide a process for effecting ring closure of polynuclear aromatic compounds by dissolving or sus-.-

pending the same in concentrated hydrofluoric:

acid I and heating in the presence of oxidizing agents, whereby simultaneous oxidation and ring closure may be effected.

facilitated by the presence of oxidizing agents or hydrogen acceptors, which latter term is. used to designate those compounds which react with hydrogen without forming water as a by-product. In those reactions in which oxidizing agents are employed, oxidation of the ring closed molecule may also be effected by employing an excess of oxygen over thatrequired to remove the hydrogen in establishin'g'the carbon to carbon linkages.

Hydrofluoric acid has been found to be particularly suitable as a medium in which to carry out these chemical reactions. becauseit is quite unreactive, being a non-oxidizing and non-reducing medium it does not enter into side reactions with the starting materials, intermediates or final products. The hydrofluoric acid is a particularly good solvent for the higher molecular weight aromatic compounds and because of. its high vapor pressure is easily removed from the reaction mixture when the condensation has been completed.

The ring closure reactions are preferably effected at temperatures ranging from 0 to 170 C. While some condensaticns may be effected below 0 C., such low temperatures need not ordinarily be employed. At temperatures above 200 C. excessive carbonation often occurs so that such temperatures are impractical. Where temperatures appreciably above 20 C. are employed the reaction may be carried out under pressure in order to minimize losses of hydrofluoric acid. The vapor pressure of the hydrofluoric acid may, however, be lowered to some degree by adding re agents such as potassium acid fluoride, ammonium acid fluoride, etc. At the elevated temperatures specified above, the pressure of the reaction system seldom exceeds 1000 lbs. per sq. in., and for most reactions the pressure is much less. Where higher pressures are necessary the pressure may be augmented by the addition of substances, such as nitrogen, oxygen, hydrochloric acid, etc., which have vapor pressures greater than hydrofluoric acid. Even when operating at ordinary atmospheric pressures it is desirable to employ closed vessels to minimize the absorption of water and as a safety precaution.

' The amount of hydrofluoric acid to be used as the reaction medium may vary within wide lim- We have found that organic compounds capable of being converted to a higher order ringsysits. A sufiicient amount should be employed to maintain the reaction in a suitable fluid state for proper agitation. From 2 to 5 parts of hydrofluoric acid per part of combined reactants has been found to give good results. Where diluents such as potassium acid fluoride are used, less hydrofluoric acid is needed. The ring closure reactions are preferably carried out in sin-.- hydrous hydrofluoric acid although solutions of hydrofluoric acid in water varying from the constant boiling mixture (36% hydrofluoric acid, B. P. 116 at atmospheric pressure) to the anhydrous hydrofluoric acid exhibits condensing activity. For practical purposes, however, initial concentrations of higher than 60% should be employed, while concentrations 01' at least 90% are preferred.

The reaction may be carried out in vessels made of anymaterial capable of withstanding the mildly corrosive efiect oi concentrated hydrofluoric acid. For hydrofluoric acid ofgreater than 60% strength 18-8 stainless steel, ordinary high carbon steel, nickel, "Monel" metal, copper, etc., are suitable. For concentrations lower than 60%, special alloys such as "electron metal are necessary.

The ratio of oxidizing agent or hydrogen acceptor to the organic compound to be ring closed will be governed by the number. of hydrogen atoms to be removed in the reaction and by the number, if any, of hydroxyl groups to be introduced. In general, one atom of oxygen or its equivalent is needed for each carbon to carbon bond established or for each hydroxyl group.

A variety of oxidizing agents or hydrogen acceptors may be used to effect the reactions. The following illustrate the type and variety of oxidizing agents that may be employed: Meta-nitrobenzene sulfonic acid, nitrates, nitrites, chromates, chlorates, lead peroxide, manganates and permanganates, mercuric salts, metallic oxides, organic peroxides, and stannic salts. The following are illustrative of the hydrogen acceptors that may be used: Quinones such as benzoquinone, naphthoquinone, indophenol, nitriles such as benzonitrile, acetonitrile, etc., ketones such as acetone, aldehydes as benzaldehyde,

acetaldehyde, or diazo compounds as diazo benzene. In some cases, the presence of copper powder accelerates the reaction.

The following examples are given to illustrate the invention. The parts used are by weight.

Example 1 A mixture. of 5.08 parts of 1,1'-dinaphthyl, 31.5 parts manganese dioxide and 100 parts of commercial anhydrous hydrofluoric acid are heated in a steel autoclave under autogenous pressure for ihours at 150 C. The reaction'mass after cooling is run into a mixture of ice and water, and the crude perylene recovered by filtration and washed free of hydrofluoric acid. The crude product is then extracted with boiling concentrated hydrochloric acid to remove any remaining inorganic salts. In this manner, five parts of a nearly pure perylene is obtained. Upon crystallizing from xylene, pure perylene melting at 260-264 C. is obtained.

Example 2 ered by filtration, washed to remove residual suiiuric acid and dried; 21.5 parts 01' a black product which is almost completely soluble in alkaline hydrosulfite is obtained. Cotton is dyed in blue grey, navy blue or black shades from a dark red vat, depending on the concentration or the dye on the fiber. That is, a 1% dyeing produces a level blue-grey shade, a 5% dyeing produces a navy blue shade, and a black is obtained at higher concentrations.

The shade oi the dye may be altered somewhat by the amount of manganese dioxide used. One molecular equivalent of manganese dioxide for equivalent of 32-1, Bz-1'-dibenzanthronyl produces a product which dyes somewhat redder in shade, whereas 3 molecular equivalents of manganese dioxide produces a color which dyes much greener in shade.

Example 3 parts of nearly anhydrous hydrofluoric acid (containing not over 10% of water), 80 parts of potassium acid fluoride, 23 parts of 2,2'-dibenzanthronyl, 0.1 part of copper powder and 7.8 parts of manganese dioxide are placed in a steel autoclave, equipped with agitation and a cover. Over a period of 2 to 3 hours, the temperature is raised to 68 C. and after the frothing due to chemical reaction has subsided, heated at 75-85 C. for 4 hours. After cooling to room temperature, the reaction mixture is run into approximateIy 1000 parts of cold water. The product is recovered by filtration and freed of inorganic residues by digesting in 250 parts of boiling hydrochloric acid. After the product is recovered by filtration and washed free of acid, the dibenzanthrone is separated by extraction with a solution of 50 parts of sodium hydrosulfite dissolved in 500 parts of 4% sodium hydroxide solution at 65-70 for 20 minutes. The mixture is filtered and the vat filtrates oxidized with 25 parts of sodium perborate. The precipitated dye is recovered' by filtration, washed free of alkali and dried.

The condensation may also be carried out in a sealed system. A charge made up of parts of concentrated hydrofluoric acid, 23 parts of 2,2'-debenzanthronyl and 5 parts of manganese dioxide are heated in a steel autoclave at C. for 4 hours. The crude product is recovered from the reaction mixture essentially as described above.

Example 4 quantity of oxidizing agents. Other hydrogen acceptors may also be employed as suggested in Example 2. v

In the above examples substituted Bz-1,Bz-1'- dibenzanthronyls and substituted 2,2'-dibenzanthronyls may be ring closed in a similar manner provided there is no substituent present in the 2,2'- and Bz-1,Bz-1'-positions, respectively. The process is particularly suitable for the ring closure of halogen, amino, nitro-derivatives, from dibenzanthronyl series, but finds wide application in the formation of carbocyclic ring systems in general. As examples of specific instances in which this reaction may be applied for the ring closure of organic compounds capable of forming higher order ring systems, the following are cited: Bz-l-benzoyl-benzanthrone, alpha-mono-, and alpha, alpha-dibenzoylnaphthalenes, benzoylor naphthoyl-anthracenes, 3,4- dimethyl meso-benzdianthrone to anthradianthrone, henzylidine anthrone to benz-benzanthrone, etc.

Example parts of a dark yellow powder is obtained. The

melting point is above 390 C. The product gives a dark red solution in concentrated sulfuric acid,

. whereas the starting material dissolves with a green color. Cotton is dyed from an orange-red va't in attractive, yellow-brown shades of excellent tastness properties. The product is believed to be the (N) Bz-1,l'; Bz-2,2'-benzanthroneanthraquinone carbazole.

Example 6 115 parts of nearly anhydrous hydrofluoric acid, 23 parts of Bz-lf-benzanthronyl-i-aminoanthraquinone and 8.7 parts of manganese dioxide were heated together in a steel autoclave at 100 C. for 6 hours. The reaction mixture was cooled and run into 1000 parts of ice. The reaction products was recovered by filtration, washed free of acid and dried. 25 parts of a grey powder which gives a brilliant green color in concentrated sulfuric acid is obtained. The product dyes cotton in brown shades from a red vat. Qualitative tests indicate the presence of hydroxyl groups in the molecule.

The application of the process of ring closing by the removal of hydrogen in hydrofluoric'acid is not limited to this specific example, but may be applied to a wide variety of secondary aromatic amines, sulfides, sulfones, ethers, selenides, etc. Specifically, the following examples may be noted: 1,1'-dianthramide to 1,2-7,8-diphthaloyl carbazole, l,1.',4,l"-trianthrimide, 1,1',5,1"-trianthrimide, 4,5- dibenzoylamino-1,1- dianthrimide, 1,l'-5,1-trianthrimide 8'-8"-benzacridone. etc. As suggested in Example 2 a variety of hydrogen acceptors or oxidizing may be employed, if necessary, to bring about. ring closure.

By the reaction as above illustrated it is possibleto produce dihydroxydibenzanthrones in a single step from 2,2'-dibenzanthronyl; and to effect ring closure 01' 82-1, Bz-1'-dibenzanthronyls without the use of alkalinecondensing agents heretofore employed according to the prior art, thus; permitting the ring closure of derivatives of Bz-l, Bz-l'-dibenzanthronyl which could not otherwise be formed or which would be formed in very unsatisfactory purity because of the hydrolysing action 0! the caustics heretofore required. By the use of hydrofluoric acid in many cases it is also possible to materially increase the yield of the desired product. Dinaphthyl which has heretofore been ring closed to perylene in yields of only approximately 50% of theory may, by the use of hydrofluoric acid, be con- 'densed to perylene in yields of 70% and higher.

As illustrated above, the ring closure is not limited to the synthesis of isocyclic ring systems,

but may be applied equally well in the produc- 10 tion of heterocyclic ring systems. In heterocyclic ring systems hydroxyl groups may also be introduced by the use of excess oxidizing agents.

We claim: 1. The process for effecting ring closure of polynuclear aromatic compounds capable of forming higher order ring systems by ring closure thru the establishment of carbon to carbon bonds by a dehydrogenation reaction which involves the removal of only hydrogen from the molecule, which comprises carrying out the reaction in hydrofluoric acid of not less than 36% concentration.

2. The process for effecting. ring closure of polynuclear aromatic compounds capable of forming higher order ring systems by ring closure thru the establishment of carbon to carbon bonds by a dehydrogenation reaction which involves the removal of only hydrogen from the molecule, which comprises carrying out the reaction in hydrofluoric acid of not less than 60% concentration and in the presence of a compound.

of the class consisting of oxidizing agents and hydrogen acceptors.

3. The process for eflfecting ring closure of a dibenzanthronyl to a dibenzanthrone compound, which comprises carrying out the reaction in hydrofluoric acid of not less than 60% concentration.

4. The process for effecting ring closure of a dibenzanthronyl to a dibenzanthrone compound,

which comprises carrying out the reaction in hydrofluoric'acid of not less than 60% concentration and in the presence of a compound of the class consisting of oxidizing agents and hydrogen acceptors.

5. The process of claim 4 in which an oxidizing agent is employed in sufllcient excess of that required to combine with the two hydrogen atoms liberated to efl'ect oxidation of the resulting 0 product to a dihydroxy dibenzanthrone.

6. The process for preparing a perylene compound from an alpha-alpha dinaphthyl which comprises carrying out the ring closure reaction in hydrofluoric acid of not less than concentration and in the presence or a compound of the class consisting of oxidizing agents and hydrogen acceptors.

7. The process for effecting ring closure of a Bz-l benzanthronyl l amino anthraquinone which comprises carrying out the reaction in hydrofluoric acid of not less than 60% concentration.

\ 8. The process for preparing a diberfzanthrone compound from a Bz-l, Bz-l'-dibenzanthronyl which comprises carrying out the ring closure reaction in hydrofluoric acid of not less than 60% concentration and in the presence of a compound oLthe class consisting of oxidizing agents and 70 hydrogen acceptors.

- JOHN M. TINKER.

VIKTOR M. WEINMAYR. ADRIAN L. LINCH. 

